I find it unlikely that you would be getting support from australia, as I doubt japan will let you do so with an indian IC in place.
So, lets say you have 11 inf, 3 fig, 1 aa. Lets also say you manage to get some US figs over, 2.
In JP1 there are 3 inf,1 art in FIC, 2 originally, 2 from phillipines. Japan builds 3 xports, 1 arm.
In JP2 there are 11 inf in FIC (3 from china, 1 from borneo, 3 from japan), 1 art, 2 arm, 6 figs, 1 bmb. On attack the two inf from east indies could be brought in, and that battle leaves us at about 80%. Of course, if japan buys 2 bombers on round 2, then their win percentage is in the high 90’s.
Obviously you divert japan’s attention, but I still don’t think it’s worth it for the UK. Russia can definitely help out, but with the UK not dumping significant resources into europe, and the US potentially not, their front will definitely be weakened.